Eye tracking method, head-mounted display, and computer readable storage medium

ABSTRACT

The disclosure provides an eye tracking method, an head-mounted display (HMD), and a computer readable storage medium. The method includes: capturing, by the first camera, a first eye image of a first eye of a wearer of the HMD; capturing, by the second camera, a second eye image of the first eye of the wearer; constructing a first eye model of the first eye based on the first eye image and the second eye image; capturing, by the first camera, a first specific eye image of the first eye of the wearer; obtaining a plurality of first specific eye landmarks in the first specific eye image; identifying a first eye pose of the first eye of the wearer based on the first eye model and the first specific eye landmarks.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. provisionalapplication Ser. No. 62/879,639, filed on Jul. 29, 2019. The entirety ofthe above-mentioned patent application is hereby incorporated byreference herein and made a part of this specification.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to a tracking mechanism, inparticular, to an eye tracking method, a head-mounted display (HMD), anda computer readable storage medium.

2. Description of Related Art

Tracking eye movement is helpful in many situations such as HMDs or intechnologies requiring hands-free control. However, most of theconventional eye tracking technologies need to be implemented by using adepth camera for retrieving depth information, which increases the costof implementation.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an eye trackingmethod, a head-mounted display (HMD), and a computer readable storagemedium, which may be used for solving the above technical problems.

In one embodiment, the disclosure provides an eye tracking method,adapted to a head-mounted display (HMD) with a first camera and a secondcamera, including: capturing, by the first camera, a first eye image ofa first eye of a wearer of the HMD; capturing, by the second camera, asecond eye image of the first eye of the wearer; constructing a firsteye model of the first eye based on the first eye image and the secondeye image; capturing, by the first camera, a first specific eye image ofthe first eye of the wearer; obtaining a plurality of first specific eyelandmarks in the first specific eye image; identifying a first eye poseof the first eye of the wearer based on the first eye model and thefirst specific eye landmarks.

In another embodiment, the disclosure provides an eye tracking method,adapted to a head-mounted display (HMD) with a first camera, a secondcamera, and a third camera, including: capturing, by the first camera, afirst eye image of a first eye of a wearer of the HMD; capturing, by thesecond camera, a second eye image of the first eye of the wearer,wherein the first camera and the second camera are front cameras of theHMD, and the first eye image and the second eye image are capturedbefore the wearer wears the HMD; constructing a first eye model of thefirst eye based on the first eye image and the second eye image;capturing, by the third camera, a first specific eye image of the firsteye of the wearer, wherein the third camera is an eye camera inside ofthe HMD for capturing eye images of the first eye, and the firstspecific eye image is captured after the wearer wears the HMD; obtaininga plurality of first specific eye landmarks in the first specific eyeimage; identifying a first eye pose of the first eye of the wearer basedon the first eye model and the first specific eye landmarks.

In another embodiment, the disclosure provides a head-mounted display(HMD) including a first camera, a second camera, a storage circuit, anda processor. The storage circuit stores a plurality of modules. Theprocessor is coupled to the first camera, the second camera, and thestorage circuit, and accesses the modules to perform following steps:controlling the first camera to capture a first eye image of a first eyeof a wearer of the HMD; controlling the second camera to capture asecond eye image of the first eye of the wearer; constructing a firsteye model of the first eye based on the first eye image and the secondeye image; controlling the first camera to capture a first specific eyeimage of the first eye of the wearer; obtaining a plurality of firstspecific eye landmarks in the first specific eye image; identifying afirst eye pose of the first eye of the wearer based on the first eyemodel and the first specific eye landmarks.

In another embodiment, the disclosure provides a non-transitory computerreadable storage medium, recording an executable computer program to beloaded by a head-mounted display (HMD) including a first camera and asecond camera to execute steps of: capturing, by the first camera, afirst eye image of a first eye of a wearer of the HMD; capturing, by thesecond camera, a second eye image of the first eye of the wearer;constructing a first eye model of the first eye based on the first eyeimage and the second eye image; capturing, by the first camera, a firstspecific eye image of the first eye of the wearer; obtaining a pluralityof first specific eye landmarks in the first specific eye image;identifying a first eye pose of the first eye of the wearer based on thefirst eye model and the first specific eye landmarks.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 shows a schematic diagram illustrating an HMD according to anembodiment of the disclosure.

FIG. 2 shows a flow chart of the eye tracking method according to anembodiment of the disclosure.

FIG. 3 is a schematic diagram illustrating an eye tracking scenarioaccording to a first embodiment of the disclosure.

FIG. 4 shows the first eye landmarks of the first eye according to anembodiment of the disclosure.

FIG. 5 shows a schematic diagram of capturing a first specific eye imageaccording to an embodiment of the disclosure.

FIG. 6 is a schematic diagram illustrating an eye tracking scenarioaccording to the second embodiment of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

See FIG. 1, which shows a schematic diagram illustrating an HMDaccording to an embodiment of the disclosure. In FIG. 1, the HMD 100includes a first camera c₁, a second camera c₂, a storage circuit 102,and a processor 104.

The storage circuit 102 is one or a combination of a stationary ormobile random access memory (RAM), read-only memory (ROM), flash memory,hard disk, or any other similar device, and which records a plurality ofmodules that can be executed by the processor 104.

In one embodiment, the first camera c₁ and the second camera c₂ may bethe eye cameras located inside of the HMD 100 for capturing eye imagesof the wearer of the HMD. For ease of the following discussions, thefirst camera c₁ may be assumed to be designed for capturing images of afirst eye (e.g., the right eye) of the wearer when the HMD 100 is wornby the wearer, and the second camera c₂ may be assumed to be designedfor capturing images of a second eye (e.g., the left eye) of the wearerwhen the HMD 100 is worn by the wearer, but the disclosure is notlimited thereto.

In various embodiments, the first camera c₁ and the second camera c₂could be any cameras having charge coupled device (CCD) lens,complementary metal oxide semiconductor transistors (CMOS) lens, or thelike.

The processor 104 may be coupled with the storage circuit 102, the firstcamera c₁ and the second camera c₂, and the processor 104 may be, forexample, a general purpose processor, a special purpose processor, aconventional processor, a digital signal processor (DSP), a plurality ofmicroprocessors, one or more microprocessors in association with a DSPcore, a controller, a microcontroller, Application Specific IntegratedCircuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, anyother type of integrated circuit (IC), a state machine, an ARM-basedprocessor, and the like.

In the embodiments of the disclosure, the processor 104 may access themodules stored in the storage circuit 102 to implement the eye trackingmethod provided in the disclosure, which would be further discussed inthe following.

See FIG. 2, which shows a flow chart of the eye tracking methodaccording to an embodiment of the disclosure. The method of thisembodiment may be executed by the HMD 100 in FIG. 1, and the details ofeach step in FIG. 2 will be described below with the components shown inFIG. 1. In addition, for better understanding the concept of thedisclosure, FIG. 3 would be used as an example, wherein FIG. 3 is aschematic diagram illustrating an eye tracking scenario according to afirst embodiment of the disclosure.

In the following discussions, the mechanism for performing eye trackingto the first eye would be explained, and the mechanism for performingeye tracking to the second eye may be understood based on the sameteachings.

Specifically, in step S210, the processor 104 may control the firstcamera c₁ to capture a first eye image EM1 of a first eye 311 of awearer 199 of the HMD 100. In step S220, the processor 104 may controlthe second camera c₂ to capture a second eye image EM2 of the first eye311 of the wearer 199. That is, both of the first camera c₁ and thesecond camera c₂ are used to capture eye images of the same eye (i.e.,the first eye 311). For implementing the steps S210 and S220, the firsteye image EM1 and the second eye image EM2 may be captured before thewearer 199 wears the HMD 100. For example, the wearer 199 may hold theHMD 100 in front of his/her face for the first camera c₁ and the secondcamera c₂ to respectively capture the first eye image EM1 and the secondeye image EM2 of the first eye 311, but the disclosure is not limitedthereto.

In some other embodiments, the first eye image EM1 and the second eyeimage EM2 may be captured with cameras c₃ and c₄, which may be the frontcameras of the HMD 100, and the details would be discussed with a secondembodiment of the disclosure.

After retrieving the first eye image EM1 and the second eye image EM2,the processor 104 may perform step S230 to construct a first eye modelof the first eye 311 based on the first eye image EM1 and the second eyeimage EM2.

In one embodiment, the processor 104 may input the first eye image EM1to a 2D eye landmark detection model, wherein the 2D eye landmarkdetection model may output a first tensor in response to the first eyeimage EM1, and the first tensor may indicate a 2D position of each of aplurality of first landmarks in the first eye image EM1. In oneembodiment, the 2D eye landmark detection model may be a convolutionalneural network (CNN) pre-trained for obtaining eye landmarks in thereceived image (e.g., the first eye image EM1).

In one embodiment, the first tensor may be a matrix with a dimension ofW×H×C, wherein W may be the width of the first eye image EM1 and H maybe the height of the first eye image EM1. In one embodiment, C may be apredetermined number of the first landmarks in the first eye image EM1,which may be also regarded as the number of channels in the first eyeimage EM1. That is, the first tensor may be regarded as including Cchannels, wherein the channels one-to-one correspond to the firstlandmarks, and each channel is a W×H matrix.

In one embodiment, each channel indicates the probability distributionof the corresponding first landmark in the first eye image EM1. Forexample, for an i-th first landmark, the corresponding channel wouldhave a certain matrix element having maximum value, wherein the positionof this matrix element in the channel indicates the position of the i-thfirst landmark in the first eye image EM1.

Similarly, the processor 104 may input the second eye image EM2 to the2D eye landmark detection model, wherein the 2D eye landmark detectionmodel outputs a second tensor in response to the second eye image EM2,the second tensor indicates a 2D position of each of a plurality ofsecond landmarks in the second eye image EM2. The details of the secondtensor may be referred to the discussions of the first tensor, whichwould not be repeated herein.

In one embodiment, the second landmarks may one-to-one correspond to thefirst landmarks. Specifically, the i-th second landmark and the i-thfirst landmark correspond to the same landmark in the first eye 311.Therefore, the i-th channel in the first tensor and the i-th channel inthe second tensor correspond to the same landmark in the first eye 311.

In this case, the processor 104 may obtaining a 3D position of each of aplurality of first eye landmarks of the first eye 311 of the wearer 199based on the first landmarks, the second landmarks, and a plurality ofcamera geometry parameters of the first camera c₁ and the second camerac₂, and accordingly constructing the first eye model of the first eye311.

In one embodiment, the camera geometry parameters of the first camera c₁and the second camera c₂ may include various external parameters andinternal parameters of the first camera c₁ and the second camera c₂, butthe disclosure is not limited thereto.

With the camera geometry parameters, the 3D position of each of aplurality of first eye landmarks of the first eye 311 may be obtainedthrough the triangulation methods in multi-view geometry, and thedetails there of may be referred to “Richard Hartley and AndrewZisserman (2003). Multiple View Geometry in computer vision. CambridgeUniversity Press. ISBN 978-0-521-54051-3”, which would not be repeatedherein.

See FIG. 4, which shows the first eye landmarks of the first eyeaccording to an embodiment of the disclosure. In FIG. 4, the first eye311 may be labelled with a predetermined number (i.e., C) of first eyelandmarks (illustrated as hollowed circles), and the 3D position of eachfirst eye landmark may be used constructing the first eye model of thefirst eye 311. In one embodiment, the first eye model may include thephysical dimension of the iris, pupil and eyelid of the first eye 311,but the disclosure is not limited thereto.

After obtaining the first eye model of the first eye 311, the processor104 may perform step S240 to control the first camera c₁ to capture afirst specific eye image of the first eye 311 of the wearer 199. In oneembodiment, the first specific eye image may be captured after thewearer 199 wears the HMD 100.

See FIG. 5, which shows a schematic diagram of capturing a firstspecific eye image according to an embodiment of the disclosure. In FIG.4, it is assumed that the wearer 199 has worn the HMD 100, and hence thefirst camera c₁ may be used to capture a first specific eye image SM1 ofthe first eye 311 as the first camera c₁ was designed for.

Next, in step S250, the processor 104 may obtain a plurality of firstspecific eye landmarks (which may be 2D eye landmarks) in the firstspecific eye image SM1. In one embodiment, the processor 104 may inputthe first specific eye image SM1 to the 2D eye landmark detection model,wherein the 2D eye landmark detection model may output a first specifictensor in response to the first specific eye image SM1, and the firstspecific tensor may indicate a 2D position of each of the first specificeye landmarks in the first specific eye image SM1. The details of thefirst specific tensor may be referred to the discussions of the firsttensor and the second tensor, which would not be repeated herein.

Afterwards, in step S260, the processor 104 may identify a first eyepose of the first eye 311 of the wearer 199 based on the first eye modeland the first specific eye landmarks. In one embodiment, the processor104 may retrieve a 3D position of each first specific eye landmarks byusing a Project N points (PNP) algorithm based on the first eye modeland the first specific eye landmarks. Details of the PNP algorithm maybe referred to related technical documents, which would not be repeatedherein.

Next, the processor 104 may identify the first eye pose based on the 3Dposition of each first specific eye landmarks. Specifically, theprocessor 104 may use the PNP algorithm to estimate position andorientation of the first specific eye landmarks including pupil, iris,eyelid. In various embodiments, the pupil size will vary in real timewhile the iris and eyelid remained unchanged, so the distance isestimated from the unchanged size feature then the pupil size can beestimated from the ellipse captured in the first specific eye image SM1,but the disclosure is not limited thereto.

In brief, the method provided in the disclosure may be regarded asincluding two stages, wherein a first stage includes steps S210-S230,and a second stage includes steps S240-S260. In the first stage, thefirst eye model of the first eye 311 may be constructed based on thefirst eye image EM1 and the second eye image EM2 captured before thewearer 199 wears the HMD 100. In the second stage, the first eye pose ofthe first eye 311 may be identified based on the first eye model and thefirst specific eye landmarks found in the first specific eye imagecaptured after the wearer 199 has worn the HMD 100. In this case, thefirst eye model of the first eye 311 may be constructed without anydepth information, and hence there is no need to dispose any depthcamera for providing depth information for performing eye tracking.Therefore, the disclosure has provided a novel way to perform eyetracking, and the cost of implementing eye tracking may be reduced.

In one embodiment, for performing eye tracking to the second eye 312 ofthe wearer 199, the processor 104 may be configured to: control thefirst camera c₁ to capture third eye image of the second eye 312 of thewearer 199 of the HMD 100; control the second camera c₂ to capture afourth eye image of the second eye 312 of the wearer 199. Similar to thefirst eye image EM1 and the second eye image EM2, the third eye imageand the fourth eye image may be captured before the wearer 199 wears theHMD 100. Next, the processor 104 may construct a second eye model of thesecond eye 312 based on the third eye image and the fourth eye image,and the details thereof may be referred to the teachings related to thefirst stage in previous embodiments, which would not be repeated herein.

Afterwards, the processor 104 may control the second camera c₂ tocapture a second specific eye image of the second eye 312 of the wearer199, wherein the second specific eye image may be captured after thewearer 199 wears the HMD 100. With the second specific eye image, theprocessor 104 may obtain a plurality of second specific eye landmarks inthe second specific eye image and identify a second eye pose of thesecond eye 312 of the wearer 199 based on the second eye model and thesecond specific eye landmarks. The details of these steps may bereferred to the teachings related to the second stage in previousembodiments, which would not be repeated herein.

In some embodiments, since the first eye image EM1 and the second eyeimage EM2 may be captured before the wearer 199 wears the HMD 100, thefirst eye image EM1 and the second eye image EM2 may be captured by thefront cameras of the HMD 100 as mentioned in the above.

See FIG. 6, which is a schematic diagram illustrating an eye trackingscenario according to the second embodiment of the disclosure.Specifically, in the second embodiment, the processor 104 may beconfigured to: control the camera c₃ to capture the first eye image EM1of the first eye 311 of the wearer 199 of the HMD 100 and control thecamera c₄ to capture the second eye image EM2 of the first eye 311 ofthe wearer 199. Similar to the first embodiment, the first eye image EM1and the second eye image EM2 may be captured before the wearer 199 wearsthe HMD 100. For example, the wearer 199 may hold the HMD 100 in frontof his/her face for the camera c₃ and the camera c₄ to respectivelycapture the first eye image EM1 and the second eye image EM2 of thefirst eye 311, but the disclosure is not limited thereto. With the firsteye image EM1 and the second eye image EM2, the processor 104 mayconstruct the first eye model of the first eye 311 based on the firsteye image EM1 and the second eye image EM2, and the details thereof maybe referred to the teachings related to the first stage in the firstembodiment, which would not be repeated herein.

In the second embodiment, after the wearer 199 wears the HMD 100, theprocessor 104 may control the first camera c₁ to capture the firstspecific eye image SM1 of the first eye 311 of the wearer as shown inFIG. 5. Next, the processor 104 may be configured to: obtain the firstspecific eye landmarks in the first specific eye image SM1 and identifythe first eye pose of the first eye 311 of the wearer 199 based on thefirst eye model and the first specific eye landmarks. The relateddetails may be referred to the teachings of the second stage in thefirst embodiment, which would not be repeated herein.

In addition, the second eye pose of the second eye 312 may be identifiedbased on the teachings in the above, which would not be repeated herein.

The disclosure further provides a computer readable storage medium forexecuting the eye tracking method. The computer readable storage mediumis composed of a plurality of program instructions (for example, asetting program instruction and a deployment program instruction)embodied therein. These program instructions can be loaded into the HMD100 and executed by the same to execute the eye tracking method and thefunctions of the HMD 100 described above.

In summary, in the first stage of the provided method, the eye model ofthe considered eye may be constructed based on the eye images capturedbefore the wearer wears the HMD. In the second stage of the providedmethod, the eye pose of the considered eye may be identified based onthe eye model and the specific eye landmarks found in the specific eyeimage captured after the wearer has worn the HMD. With the two stages,the eye model of the considered eye may be constructed without any depthinformation, and hence there is no need to dispose any depth camera forproviding depth information for performing eye tracking. Therefore, thedisclosure has provided a novel way to perform eye tracking, and thecost of implementing eye tracking may be reduced.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. An eye tracking method, adapted to a head-mounteddisplay (HMD) with a first camera and a second camera, comprising:capturing, by the first camera, a first eye image of a first eye of awearer of the HMD; capturing, by the second camera, a second eye imageof the first eye of the wearer; constructing a first eye model of thefirst eye based on the first eye image and the second eye image;capturing, by the first camera, a first specific eye image of the firsteye of the wearer; obtaining a plurality of first specific eye landmarksin the first specific eye image; and identifying a first eye pose of thefirst eye of the wearer based on the first eye model and the firstspecific eye landmarks.
 2. The method according to claim 1, wherein thefirst eye image and the second eye image are captured before the wearerwears the HMD.
 3. The method according to claim 1, wherein the firstspecific eye image is captured after the wearer wears the HMD.
 4. Themethod according to claim 1, wherein the step of constructing the firsteye model of the first eye based on the first eye image and the secondeye image comprising: inputting the first eye image to a 2D eye landmarkdetection model, wherein the 2D eye landmark detection model outputs afirst tensor in response to the first eye image, and the first tensorindicates a 2D position of each of a plurality of first landmarks in thefirst eye image; inputting the second eye image to the 2D eye landmarkdetection model, wherein the 2D eye landmark detection model outputs asecond tensor in response to the second eye image, the second tensorindicates a 2D position of each of a plurality of second landmarks inthe second eye image, wherein the second landmarks one-to-onecorresponds to the first landmarks; and obtaining a 3D position of eachof a plurality of first eye landmarks of the first eye of the wearerbased on the first landmarks, the second landmarks, and a plurality ofcamera geometry parameters of the first camera and the second camera,and accordingly constructing the first eye model of the first eye. 5.The method according to claim 4, wherein the step of obtaining the firstspecific eye landmarks in the first specific eye image comprising:inputting the first specific eye image to the 2D eye landmark detectionmodel, wherein the 2D eye landmark detection model outputs a firstspecific tensor in response to the first specific eye image, and thefirst specific tensor indicates a 2D position of each of the firstspecific eye landmarks in the first specific eye image.
 6. The methodaccording to claim 1, wherein the first specific eye landmarks in thefirst specific eye image are 2D eye landmarks.
 7. The method accordingto claim 1, wherein the step of identifying the first eye pose of thefirst eye of the wearer based on the first eye model and the firstspecific eye landmarks comprising: retrieving a 3D position of each ofthe first specific eye landmarks by using a Project N points (PNP)algorithm based on the first eye model and the first specific eyelandmarks; and identifying the first eye pose based on the 3D positionof each of the first specific eye landmarks.
 8. The method according toclaim 1, further comprising: capturing, by the first camera, a third eyeimage of a second eye of the wearer of the HMD; capturing, by the secondcamera, a fourth eye image of the second eye of the wearer, wherein thethird eye image and the fourth eye image are captured before the wearerwears the HMD; constructing a second eye model of the second eye basedon the third eye image and the fourth eye image; capturing, by thesecond camera, a second specific eye image of the second eye of thewearer, wherein the second specific eye image is captured after thewearer wears the HMD; obtaining a plurality of second specific eyelandmarks in the second specific eye image; and identifying a second eyepose of the second eye of the wearer based on the second eye model andthe second specific eye landmarks.
 9. The method according to claim 1,wherein the first camera and the second camera are eye cameras inside ofthe HMD, the first camera is used for capturing eye images of the firsteye, and the second camera is used for capturing eye images of thesecond eye.
 10. An eye tracking method, adapted to a head-mounteddisplay (HMD) with a first camera, a second camera, and a third camera,comprising: capturing, by the first camera, a first eye image of a firsteye of a wearer of the HMD; capturing, by the second camera, a secondeye image of the first eye of the wearer, wherein the first camera andthe second camera are front cameras of the HMD, and the first eye imageand the second eye image are captured before the wearer wears the HMD;constructing a first eye model of the first eye based on the first eyeimage and the second eye image; capturing, by the third camera, a firstspecific eye image of the first eye of the wearer, wherein the thirdcamera is an eye camera inside of the HMD for capturing eye images ofthe first eye, and the first specific eye image is captured after thewearer wears the HMD; obtaining a plurality of first specific eyelandmarks in the first specific eye image; and identifying a first eyepose of the first eye of the wearer based on the first eye model and thefirst specific eye landmarks.
 11. A head-mounted display (HMD),comprising: a first camera; a second camera; a storage circuit, storinga plurality of modules; and a processor, coupled to the first camera,the second camera, and the storage circuit, and accessing the modules toperform following steps: controlling the first camera to capture a firsteye image of a first eye of a wearer of the HMD; controlling the secondcamera to capture a second eye image of the first eye of the wearer;constructing a first eye model of the first eye based on the first eyeimage and the second eye image; controlling the first camera to capturea first specific eye image of the first eye of the wearer; obtaining aplurality of first specific eye landmarks in the first specific eyeimage; and identifying a first eye pose of the first eye of the wearerbased on the first eye model and the first specific eye landmarks. 12.The HMD according to claim 11, wherein the first eye image and thesecond eye image are captured before the wearer wears the HMD.
 13. TheHMD according to claim 11, wherein the first specific eye image iscaptured after the wearer wears the HMD.
 14. The HMD according to claim11, wherein the processor is configured to: input the first eye image toa 2D eye landmark detection model, wherein the 2D eye landmark detectionmodel outputs a first tensor in response to the first eye image, and thefirst tensor indicates a 2D position of each of a plurality of firstlandmarks in the first eye image; input the second eye image to the 2Deye landmark detection model, wherein the 2D eye landmark detectionmodel outputs a second tensor in response to the second eye image, thesecond tensor indicates a 2D position of each of a plurality of secondlandmarks in the second eye image, wherein the second landmarksone-to-one corresponds to the first landmarks; and obtaining a 3Dposition of each of a plurality of first eye landmarks of the first eyeof the wearer based on the first landmarks, the second landmarks, and aplurality of camera geometry parameters of the first camera and thesecond camera, and accordingly constructing the first eye model of thefirst eye.
 15. The HMD according to claim 14, wherein the processor isconfigured to: input the first specific eye image to the 2D eye landmarkdetection model, wherein the 2D eye landmark detection model outputs afirst specific tensor in response to the first specific eye image, andthe first specific tensor indicates a 2D position of each of the firstspecific eye landmarks in the first specific eye image.
 16. The HMDaccording to claim 11, wherein the first specific eye landmarks in thefirst specific eye image are 2D eye landmarks.
 17. The HMD according toclaim 11, wherein processor is configured to: retrieve a 3D position ofeach first specific eye landmarks by using a Project N points (PNP)algorithm based on the first eye model and the first specific eyelandmarks; identify the first eye pose based on the 3D position of eachfirst specific eye landmarks.
 18. The HMD according to claim 11, whereinthe processor is further configured to: controlling the first camera tocapture third eye image of a second eye of the wearer of the HMD;controlling the second camera to capture a fourth eye image of thesecond eye of the wearer, wherein the third eye image and the fourth eyeimage are captured before the wearer wears the HMD; constructing asecond eye model of the second eye based on the third eye image and thefourth eye image; controlling the second camera to capture a secondspecific eye image of the second eye of the wearer, wherein the secondspecific eye image is captured after the wearer wears the HMD; obtaininga plurality of second specific eye landmarks in the second specific eyeimage; and identifying a second eye pose of the second eye of the wearerbased on the second eye model and the second specific eye landmarks. 19.The HMD according to claim 11, wherein the first camera and the secondcamera are eye cameras inside of the HMD, the first camera is used forcapturing eye images of the first eye, and the second camera is used forcapturing eye images of the second eye.
 20. A non-transitory computerreadable storage medium, recording an executable computer program to beloaded by a head-mounted display (HMD) comprising a first camera and asecond camera to execute steps of: capturing, by the first camera, afirst eye image of a first eye of a wearer of the HMD; capturing, by thesecond camera, a second eye image of the first eye of the wearer;constructing a first eye model of the first eye based on the first eyeimage and the second eye image; capturing, by the first camera, a firstspecific eye image of the first eye of the wearer; obtaining a pluralityof first specific eye landmarks in the first specific eye image; andidentifying a first eye pose of the first eye of the wearer based on thefirst eye model and the first specific eye landmarks.